Head mounted image display device and display device

ABSTRACT

There is provided an image display device including (A) an image forming device, (B) an optical device configured to receive incident light output from the image forming device and output the incident light, and (C) a light receiving device configured to detect the light output from the image forming device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Priority PatentApplication JP 2014-023137 filed Feb. 10, 2014, the entire contents ofwhich are incorporated herein by reference.

BACKGROUND

The present disclosure relates to an image display device and a displaydevice including a relevant image display device, and more particularly,to a display device used as a head mounted display (HMD) and an imagedisplay device used in a relevant display device.

A virtual display device (image display device) for allowing an observerto observe a two-dimensional (2D) image formed by an image formingdevice as a virtual image enlarged by a virtual image optical system iswell known, for example, from Japanese Patent Application PublicationNo. 2006-162767.

As illustrated in a conceptual diagram of FIG. 22, an image displaydevice 100′ includes an image forming device 111 having a plurality ofpixels arranged in a 2D matrix, a collimating optical system 112, whichcollimates light output from a pixel of the image forming device 111into parallel light, and an optical device (a light guide device) 120 onwhich the parallel light from the collimating optical system 112 isincident, through which the light is guided, and from which the light isoutput. The optical device 120 includes a light guide plate 121, whichoutputs the incident light after the incident light propagates throughthe inside according to total reflection, a first polarizing unit 130(for example, including a light reflecting film of one layer), whichreflects the light incident on the light guide plate 121 so that thelight incident on the light guide plate 121 is totally reflected insidethe light guide plate 121, and a second polarizing unit 140 (forexample, including a light reflecting multi-film having a multi-layerlaminated structure), which outputs from the light guide plate 121 thelight propagating through the inside of the light guide plate 121according to the total reflection. A weight and size of a device can bereduced, for example, when the HMD is formed according to such an imagedisplay device 100′. Here, reference numerals representing the othercomponents in FIG. 22 can be found with reference to an image displaydevice according to Embodiment 1 which will be described with referenceto FIG. 1.

Alternatively, in order to allow an observer to observe a 2D imageformed by the image forming device as a virtual image enlarged by thevirtual image optical system, a virtual image display device (imagedisplay device) using hologram diffraction gratings is well known, forexample, from Japanese Patent Application Publication No. 2007-094175.

As illustrated in a conceptual diagram of FIG. 23, an image displaydevice 300′ basically includes an image forming device 111, whichdisplays an image, a collimating optical system 112, and an opticaldevice (a light guide device) 320 on which light displayed on the imageforming device 111 is incident and through which the incident light isguided to a pupil 21 of the observer. Here, the optical device 320includes a light guide plate 321 and a first diffraction grating member330 and a second diffraction grating member 340 formed by reflectivevolume hologram diffraction gratings provided on the light guide plate321. Light output from each pixel of the image forming device 111 isincident on the collimating optical system 112, and a plurality beams ofparallel light having different angles at which the parallel light isincident on the light guide plate 321 is generated by the collimatingoptical system 112, and incident on the light guide plate 321. Theparallel light is incident on and output from a first surface 322 of thelight guide plate 321. On the other hand, the first diffraction gratingmember 330 and the second diffraction grating member 340 are mounted ona second surface 323 of the light guide plate 321 parallel to the firstsurface 322 of the light guide plate 321. Here, reference numeralsrepresenting the other components of FIG. 23 can be found with referenceto an image display device according to Embodiment 4 which will bedescribed with reference to FIG. 7.

SUMMARY

Meanwhile, in the image display device, for example, if the light guideplate gets dirty or the light source constituting the image formingdevice is temporally degraded, light intensity of an image reaching theobserver is reduced, and, for example, if deviation or the like occursin the optical system of the image display device, the light intensityof an image reaching the observer is reduced, or an image quality of theimage observed by the observer is reduced. Further, depending on thelight source equipped in the image forming device, a wavelength of lightoutput from the light source changes due to heat generation of the lightsource, and an image quality of an image observed by an observer may beconsequently lowered. However, in the head mounted display of therelated art, it is difficult to detect the occurrence of an abnormalityin the image display device or to detect a variation in a wavelength oflight output from the light source.

Thus, it is desirable to provide an image display device having aconfiguration and structure capable of easily detecting the occurrenceof an abnormality in the image display device and a display deviceincluding a relevant image display device. It is also desirable toprovide an image display device having a configuration and structurecapable of easily detecting a variation in a wavelength of light outputfrom the light source and a display device including a relevant imagedisplay device.

According to an embodiment of the present disclosure, there is providedan image display device including (A) an image forming device, (B) anoptical device configured to receive incident light output from theimage forming device and output the incident light, and (C) a lightreceiving device configured to detect the light output from the imageforming device.

According to another embodiment of the present disclosure, there isprovided a display device including (I) a frame to be mounted on a headof an observer, and (II) an image display device mounted on the frame,the image display device including (A) an image forming device, (B) anoptical device configured to receive incident light output from theimage forming device and outputs the incident light, and (C) a lightreceiving device configured to detect the light output from the imageforming device. That is to say, the image display device in the displaydevice according to an embodiment of the present disclosure includes theimage display device according to an embodiment of the presentdisclosure.

According to still another embodiment of the present disclosure, thereis provided an image display device including (A) an image formingdevice configured to include a liquid crystal display device and a lightsource, (B) a light guide plate configured to propagate light outputfrom the image forming device, and (C) a light receiving deviceconfigured to detect part of light output from the image forming device.A wavelength of light output from the light source is controlled basedon a detection result of the light receiving device.

According to one or more of embodiments of the present disclosure, theimage display device or the display device of an embodiment of thepresent disclosure is provided with a light receiving device thatdetects light output from an image forming device, and thus it ispossible to immediately detect whether or not an image to be displayedon an image display device or light output from an optical device isabnormal with a high degree of accuracy. Here, the effects described inthis specification are merely exemplary and not limited, and there maybe additional effects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram of an image display device in a displaydevice of Embodiment 1;

FIG. 2 is a schematic top view of the display device of Embodiment 1;

FIG. 3 is a schematic front view illustrating the display device ofEmbodiment 1;

FIG. 4 is a schematic side view illustrating the display device ofEmbodiment 1;

FIG. 5 is a diagram schematically illustrating propagation of light in alight guide plate constituting an image display device;

FIG. 6 is a conceptual diagram of an image display device in a displaydevice of Embodiment 3;

FIG. 7 is a conceptual diagram of an image display device in a displaydevice of Embodiment 4;

FIG. 8 is a schematic cross-sectional view illustrating an enlargedportion of a reflective volume hologram diffraction grating in a displaydevice of Embodiment 4;

FIG. 9 is a conceptual diagram of an image display device in a displaydevice of Embodiment 5;

FIG. 10 is a conceptual diagram of an image display device in a displaydevice of Embodiment 6, and illustrates a modification of the displaydevice of Embodiment 1;

FIG. 11 is a conceptual diagram of an image display device in a displaydevice of Embodiment 6, and illustrates a modification of the displaydevice of Embodiment 4;

FIG. 12 is a conceptual diagram of an image display device in a displaydevice of Embodiment 8, and illustrates a modification of the displaydevice of Embodiment 1;

FIG. 13 is a conceptual diagram of an image display device in a displaydevice of Embodiment 8, and illustrates a modification of the displaydevice of Embodiment 4;

FIG. 14 is a conceptual diagram of a part of an optical device in adisplay device of Embodiment 10;

FIG. 15 is a schematic front view of a display device of Embodiment 11;

FIG. 16 is a schematic top view of the display device of Embodiment 11;

FIG. 17 is a conceptual diagram of a modified example of an imageforming device;

FIG. 18 is a conceptual diagram illustrating another modified example ofan image forming device;

FIG. 19 is a conceptual diagram illustrating another modified example ofan image forming device;

FIG. 20 is a conceptual diagram illustrating another modified example ofan image forming device;

FIG. 21 is a conceptual diagram illustrating another modified example ofan image forming device;

FIG. 22 is a conceptual diagram of an image display device in a displaydevice according to a related art; and

FIG. 23 is a conceptual diagram of an image display device in a modifiedexample of the display device according to the related art.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail with reference to the appended drawings. Note that,in this specification and the appended drawings, structural elementsthat have substantially the same function and structure are denoted withthe same reference numerals, and repeated explanation of thesestructural elements is omitted.

Hereinafter, embodiments of the present disclosure will be describedwith reference to the appended drawings, but the present disclosure isnot limited to the following embodiments, and various numerical valuesor materials in the following embodiments are exemplary. The descriptionwill proceed in the following order.

1. Overall description of display device and image display device ofpresent disclosure

2. Embodiment 1 (display device and image display device: first andthird forms of image display devices of present disclosure)

3. Embodiment 2 (modification of Embodiment 1: fourth and sixth forms ofimage display devices)

4. Embodiment 3 (modifications of Embodiment 1 and Embodiment 2)

5. Embodiment 4 (other modifications of Embodiment 1 and Embodiment 2)

6. Embodiment 5 (modification of Embodiment 4)

7. Embodiment 6 (modifications of Embodiment 1 and Embodiments 3 to 5:second and third forms of image display devices)

8. Embodiment 7 (modification of Embodiment 6: fifth and sixth forms ofimage display devices)

9. Embodiment 8 (modifications of Embodiment 1 and Embodiments 3 to 5:third form of image display device)

10. Embodiment 9 (modification of Embodiment 8: sixth form of imagedisplay device)

11. Embodiment 10 (modifications of Embodiments 1 to 9: third and sixthforms of image display devices)

12. Embodiment 11 (other modifications of Embodiments 1 to 9) and others

[Overall Description of Display Device and Image Display Device ofPresent Disclosure]

In the image display device or the image display device in the displaydevice (which will be generically referred to be “image display deviceaccording to an embodiment of the present disclosure or the like”)according to an embodiment of the present disclosure, the optical devicecan include (a) a light guide plate configured to cause the incidentlight to propagate inside the light guide plate according to totalreflection and then output the incident light, (b) a first polarizingunit configured to polarize the light incident on the light guide plateso that the light incident on the light guide plate is totally reflectedinside the light guide plate, and (c) a second polarizing unitconfigured to polarize the light propagating inside the light guideplate according to total reflection to output part of light propagatinginside the light guide plate according to total reflection from thelight guide plate, the second polarizing unit including a first portionthat polarizes the light propagating inside the light guide plateaccording to total reflection toward an observer, and a second portionthat polarizes the light propagating inside the light guide plateaccording to total reflection toward the light receiving device. Forconvenience, this image display device is referred to as the “first formof image display device.” The term “total reflection” means internaltotal reflection or total reflection inside the light guide plate.Hereinafter, the same is also true.

Alternatively, in the image display device according to an embodiment ofthe present disclosure or the like, the optical device can include (a) alight guide plate configured to cause the incident light to propagateinside the light guide plate according to total reflection and thenoutput the incident light, (b) a first polarizing unit configured topolarize the light incident on the light guide plate so that the lightincident on the light guide plate is totally reflected inside the lightguide plate, and (c) a second polarizing unit configured to polarize thelight propagating inside the light guide plate according to totalreflection to output part of light propagating inside the light guideplate according to total reflection from the light guide plate. Thelight receiving device can be arranged on an end portion of the lightguide plate at a side of the second polarizing unit. For convenience,this image display device is referred to as the “second form of imagedisplay device.”

In the first and second forms of image display devices and fourth andfifth forms of image display devices to be described later, the firstpolarizing unit may be configured to reflect all light incident on thelight guide plate or reflect part of light incident on the light guideplate, and the second polarizing unit may be configured to transmit andreflect light propagating inside the light guide plate according tototal reflection. In other words, in this case, the first polarizingunit functions as a reflecting mirror or a semi-transmissive mirror, andthe second polarizing unit functions as a semi-transmissive mirror.Here, the second polarizing unit may be configured with a reflectivevolume hologram diffraction grating. Here, according to circumstances,in the first form of image display device and the fourth form of imagedisplay device to be described later, the second polarizing unit may beconfigured to output all light propagating inside the light guide plateaccording to total reflection from the light guide plate.

Alternatively, in the image display device according to an embodiment ofthe present disclosure or the like, the optical device can include alight semi-reflecting member that reflects part of light output from theimage forming device and transmits a remaining part. The light receivingdevice can detect the light passing through the light semi-reflectingmember. For convenience, this image display device is referred to as the“third form of image display device.”

In the third form of image display device and the sixth form of imagedisplay device to be described later, the light semi-reflecting membermay be configured with the first polarizing unit or may be configuredwith the second polarizing unit.

Alternatively, in the third form of image display device and the sixthform of image display device to be described later, the lightsemi-reflecting member may be configured with a concave mirror thatreflects light from the image forming device. In this case, the opticaldevice preferably includes a semi-transmissive mirror that outputs lightreflected by the concave mirror toward the observer and a quarterwavelength plate arranged between the semi-transmissive mirror and theconcave mirror. Preferably, the concave mirror is configured to transmitpart of light incident on the concave mirror (that is, the concavemirror is configured with a semi-transmissive concave mirror), and thelight receiving device is arranged to receive light passing through theconcave mirror.

Alternatively, in the image display device of an embodiment of thepresent disclosure or the like, the light receiving device may employ aform in which the light receiving device is optically connected to theoptical device. In other words, not only a form in which the lightreceiving device is connected to the optical device directly but also aform in which the light receiving device is connected to the opticaldevice through an adhesive member, a light guide member, or the like sothat light is input is also included.

Further, in the image display device of an embodiment of the presentdisclosure or the like having various kinds of preferred forms andconfigurations, a configuration in which an operation of the imageforming device is controlled based on the detection result of the lightreceiving device may be provided. In this case, a configuration in whicha position of an image output from the image forming device iscontrolled based on the detection result of the light receiving deviceor a configuration in which an output angle of light output from theoptical device is controlled based on the detection result of the lightreceiving device may be provided. Alternatively, in order to compensatefor distortion occurring in an image output from the optical device, aconfiguration in which a signal for compensating for distortionoccurring in an image is weighted to an image signal to be transmittedto the image forming device, that is, a configuration in which a signalfor compensating for distortion occurring in an image output from theoptical device is transmitted to the image forming device based on thedetection result of the light receiving device, may be provided.

Alternatively, in the image display device according to an embodiment ofthe present disclosure or the like, the image forming device can includea light source configured with a GaN semiconductor laser element. Theoptical device can include (a) a light guide plate configured to causethe incident light to propagate inside the light guide plate accordingto total reflection and then output the incident light, (b) a firstpolarizing unit configured to polarize the light incident on the lightguide plate so that the light incident on the light guide plate istotally reflected inside the light guide plate, the first polarizingunit being configured with a reflecting mirror or a semi-transmissivemirror, and (c) a second polarizing unit configured to polarize thelight propagating inside the light guide plate according to totalreflection to output part of light propagating inside the light guideplate according to total reflection from the light guide plate, thesecond polarizing unit being configured with a reflective volumehologram diffraction grating, the second polarizing unit including afirst portion that polarizes the light propagating inside the lightguide plate according to total reflection toward an observer, and asecond portion that polarizes the light propagating inside the lightguide plate according to total reflection toward the light receivingdevice. A wavelength of light output from the light source is controlledbased on a detection result of the light receiving device.

Alternatively, in the image display device according to an embodiment ofthe present disclosure or the like, the image forming device can includea light source configured with a GaN semiconductor laser element. Theoptical device can include (a) a light guide plate configured to causethe incident light to propagate inside the light guide plate accordingto total reflection and then output the incident light, (b) a firstpolarizing unit configured to polarize the light incident on the lightguide plate so that the light incident on the light guide plate istotally reflected inside the light guide plate, the first polarizingunit being configured with a reflecting mirror or a semi-transmissivemirror, and (c) a second polarizing unit configured to polarize thelight propagating inside the light guide plate according to totalreflection to output part of light propagating inside the light guideplate according to total reflection from the light guide plate, thesecond polarizing unit being configured with a reflective volumehologram diffraction grating. The light receiving device can be arrangedon an end portion of the light guide plate at a side of the secondpolarizing unit. A wavelength of light output from the light source canbe controlled based on a detection result of the light receiving device.

Alternatively, in the image display device according to an embodiment ofthe present disclosure or the like, the image forming device can includea light source configured with a GaN semiconductor laser element. Theoptical device can include a light semi-reflecting member that reflectspart of light output from the image forming device and transmits aremaining part. The light receiving device can detect the light passingthrough the light semi-reflecting member, and controls a wavelength oflight output from the light source based on a detection result. Forconvenience, this image display device is referred to as the “sixth formof image display device.”

Further, in the image display device of an embodiment of the presentdisclosure or the like having various kinds of preferred forms andconfigurations, the light receiving device may have a configuration inwhich the light receiving elements are arranged one-dimensionally (thatis, configured with a so-called line sensor) or a configuration in whichthe light receiving elements are arranged in a 2D matrix (that is,configured with a so-called imaging element). Here, the line sensor orthe imaging element may be configured with a solid-state imaging deviceincluding a collection of photo sensors or a CCD or CMOS sensor.

In order to detect the occurrence of an abnormality in the image displaydevice, preferably, a test signal is transmitted to the image formingdevice during one image display frame at intervals of a certain periodof time (for example, at intervals of 10 seconds or 1 minute), a testpattern is displayed on the image forming device, and the relevant testpattern is detected by the light receiving device. Alternatively,preferably, when an operation of the image display device starts orends, the test signal is transmitted to the image forming device, thetest pattern is displayed on the image forming device, and the relevanttest pattern is detected by the light receiving device. When the imagedisplay device is operating normally, the test pattern is received in acertain pixel of the light receiving device. However, when anabnormality occurs in the image display device, the test pattern isreceived in a pixel deviated from the certain pixel of the lightreceiving device. Alternatively, when an abnormality occurs in the imagedisplay device, there are also cases in which intensity of lightreceived by the light receiving device is reduced. Thus, when the lightreceiving device detects that an abnormality has occurred in the imagedisplay device, the image display device or the display device outputs awarning. Alternatively, when the test pattern is received in the pixeldeviated from the certain pixel of the light receiving device, it ispreferable to compensate an image signal to be transmitted to the imageforming device and eliminate the deviation. Alternatively, an outputangle of light output from the optical device may be controlled, and inorder to compensate for distortion occurring in an image output from theoptical device, a configuration in which a signal for compensating fordistortion occurring in an image is weighted to an image signal to betransmitted to the image forming device may be provided. Further, whenintensity of light received by the light receiving device is reduced, itis preferable to perform processing (for example, an increase in lightintensity of the light source) of increasing light intensity of an imageformed by the image forming device.

In the fourth to sixth forms of image display devices, in order todetect whether or not a wavelength of light output from the light sourcehas significantly changed, preferably, the test signal is transmitted tothe image forming device during one image display frame at intervals ofa certain period of time (for example, at intervals of 10 seconds or 1minute), the test pattern is displayed on the image forming device, andthe relevant test pattern is detected by the light receiving device.When the wavelength of light output from the light source has notsignificantly changed, the test pattern is received in the certain pixelof the light receiving device. However, when the wavelength of lightoutput from the light source has significantly changed, specifically,when the wavelength of light output from the light source has increaseddue to heat generation of the light source, the test pattern is receivedin the pixel deviated from the certain pixel of the light receivingdevice. Alternatively, there are also cases in which intensity of lightreceived by the light receiving device is reduced. Thus, when such aphenomenon is detected by the light receiving device, it is preferablethat the wavelength of light output from the light source be shifted tothe short wavelength side to return to the original wavelength byincreasing a driving current of a GaN semiconductor laser elementconstituting the light source. Here, when the GaN semiconductor laserelement is driven based on a pulse width modulation (PWM) scheme, it ispreferable to control a pulse height.

In the display device of an embodiment of the present disclosure havingvarious kinds of preferred forms and configurations, the optical devicemay be of a transmissive type or a semi-transmissive type (see-throughtype). Specifically, at least a portion of the optical device facing anobserver's pupil is configured to be transmissive or semi-transmissive(see-through), and it is possible to view an outside view through theportion of the optical device. The display device may include one imagedisplay device or two image display devices.

In this specification, the terms “semi-transmissive” and“semi-reflective” may indicate not only that ½ (50%) of incident lightis transmitted or reflected, but also that part of incident light istransmitted and the remaining part is reflected.

When the first polarizing unit reflects all light incident on the lightguide plate, for example, the first polarizing unit may be configuredwith a light reflecting film (a type of mirror) that is formed of ametal including an alloy and reflects light incident on the light guideplate. Further, when the first polarizing unit reflects part of lightincident on the light guide plate, for example, the first polarizingunit may be configured with a multi-layer laminated structure in which aplurality of dielectric laminated films are laminated, a half mirror, ora polarization beam splitter. Furthermore, the second polarizing unitmay be configured with a multi-layer laminated structure in which aplurality of dielectric laminated films are laminated, a half mirror, apolarization beam splitter, or a hologram diffraction grating film. Thefirst polarizing unit and the second polarizing unit are disposed in thelight guide plate, but in the first polarizing unit, at least part ofparallel light incident on the light guide plate is reflected ordiffracted so that the parallel light incident on the light guide plateis totally reflected inside the light guide plate. Meanwhile, in thesecond polarizing unit, parallel light propagating inside the lightguide plate according to total reflection is refracted or diffracted aplurality of times and then output from the light guide plate in aparallel light state.

Alternatively, the first polarizing unit can be configured to diffractlight incident on the light guide plate, and the second polarizing unitcan be configured to diffract light propagating through the inside ofthe light guide plate according to the total reflection. In this case,the first polarizing unit and the second polarizing unit can be formedby diffraction grating elements. Further, the diffraction gratingelement can be formed by a reflective diffraction grating element or atransmissive diffraction grating element. Alternatively, one diffractiongrating element can be formed by the reflective diffraction gratingelement and the other diffraction grating element can be formed by thetransmissive diffraction grating element. A reflective volume hologramdiffraction grating can be included as the reflective diffractiongrating element. For convenience, the first polarizing unit formed bythe reflective volume hologram diffraction grating may be referred to asa “first diffraction grating member,” and the second polarizing unitformed by the reflective volume hologram diffraction grating may bereferred to as a “second diffraction grating member.”

The image display device in accordance with the present disclosure canperform a single-color (for example, green) image display. When colorimage display is performed, P diffraction grating layers, each of whichis formed by a reflective volume hologram diffraction grating, can belaminated to cause the first diffraction grating member or the seconddiffraction grating member to cope with diffraction/reflection of Ptypes of light having P types (for example, P=3, that is, three types ofred, green, and blue) of different wavelength bands (or wavelengths).Each diffraction grating layer is provided with interference fringescorresponding to one type of wavelength band (or wavelength).Alternatively, to cope with diffraction and reflection of P types oflight having P types of different wavelength bands (or wavelengths), Ptypes of interference fringes can be configured to be formed in thefirst diffraction grating member or the second diffraction gratingmember formed by one diffraction grating layer. Alternatively, forexample, the angle of view can be divided into three equal parts, andthe first diffraction grating member or the second diffraction gratingmember can be configured by laminating diffraction grating layerscorresponding to angles of view. Alternatively, for example, a structurein which a first diffraction grating member and a second diffractiongrating member, each of which is configured with a diffraction gratinglayer formed of a reflective volume hologram diffraction grating thatdiffracts or reflects light having a red wavelength band (orwavelength), are arranged in the first light guide plate, a firstdiffraction grating member and a second diffraction grating member, eachof which is configured with a diffraction grating layer formed of areflective volume hologram diffraction grating that that diffracts orreflects light having a green wavelength band (or wavelength), arearranged in the second light guide plate, a first diffraction gratingmember and a second diffraction grating member, each of which isconfigured with a diffraction grating layer formed of a reflectivevolume hologram diffraction grating that that diffracts or reflectslight having a blue wavelength band (or wavelength), are arranged in thethird light guide plate, and the first light guide plate, the secondlight guide plate, and the third light guide plate are laminated with agap therebetween may be adopted. By adopting these configurations, it ispossible to increase the diffraction efficiency and acceptablediffraction angle and optimize the diffraction angle when light beamshaving the wavelength bands (or wavelengths) are diffracted andreflected by the first diffraction grating member or the seconddiffraction grating member. A protection member is preferably arrangedso that the reflective volume hologram diffraction gratings do not comein direct contact with the air.

The first diffraction grating member and the second diffraction gratingmember can be formed of a photopolymer material. It is only necessarythat the material and basic structure of the first diffraction gratingmember and the second diffraction grating member formed by thereflective volume hologram diffraction gratings be the same as those ofthe reflective volume hologram diffraction gratings of the related art.The reflective volume hologram diffraction grating refers to a hologramdiffraction grating that diffracts and reflects only +1-order diffractedlight. Although the diffraction grating member is provided withinterference fringes extending from the inner side to the outer side ofthe diffraction grating member, a method of forming the interferencefringes may be the same as adopted in the related art. Specifically, forexample, it is only necessary that a material (e.g., a photopolymermaterial) constituting the diffraction grating member be irradiated withobject light in a first predetermined direction on one side, a materialconstituting the diffraction grating member be simultaneously irradiatedwith reference light in a second predetermined direction on the otherside, and interference fringes formed by the object light and thereference light be recorded in the material constituting the diffractiongrating member. By appropriately selecting the first predetermineddirection, the second predetermined direction, and wavelengths of theobject light and the reference light, a desired pitch of theinterference fringes and a desired slant angle of the interferencefringes on the surfaces of the diffraction grating member can beobtained. The slant angle of the interference fringes refers to theangle formed between the surfaces of the diffraction grating member (orthe diffraction grating layer) and the interference fringes. When thefirst diffraction grating member and the second diffraction gratingmember are formed by a laminated structure in which P diffractiongrating layers, each of which is formed by a reflective volume hologramdiffraction grating, are laminated, it is only necessary to separatelymanufacture P diffraction grating layers and then laminate (adhere) theP diffraction grating layers, for example, using an ultraviolet curingresin adhesive. In addition, the P diffraction grating layers may beformed by manufacturing one diffraction grating layer using an adhesivephotopolymer material, and then adhering layers of the adhesivephotopolymer material thereon in order to manufacture diffractiongrating layers.

Alternatively, in the image display device in accordance with thepresent disclosure, the optical device can be formed by asemi-transmissive mirror on which light output from the image formingdevice is incident and from which the incident light is reflected andoutput toward the pupil of the observer. A structure in which the lightoutput from the image forming device propagates through the air and isincident on the semi-transmissive mirror may be provided. For example, astructure in which the light output from the image forming devicepropagates inside a transparent member such as a glass plate or aplastic plate (specifically, a member formed of the same material as thematerial constituting the light guide plate to be described later) andincident on a semi-transmissive mirror may be provided. Thesemi-transmissive mirror may be mounted on the image forming device viathe transparent member, and the semi-transmissive mirror may be mountedon the image forming device via a member separate from the transparentmember.

In the image display device of an embodiment of the present disclosureor the like having various kinds of preferred forms and configurations,the image forming device may be configured to include a plurality ofpixels arranged in a 2D matrix. Here, a configuration of this imageforming device is referred to as a “first form of image forming device”for convenience.

As the first form of image forming device, for example, there are animage forming device configured with a reflective spatial lightmodulating device and a light source, an image forming device configuredwith a transmissive spatial light modulating device and a light source,and an image forming device configured with a light emitting elementsuch as an organic electro luminescence (EL), an inorganic EL, or alight emitting diode (LED), but among the image forming devices, theimage forming device configured with the reflective spatial lightmodulating device and the light source is preferable. As the spatiallight modulating device, a light valve, a transmissive or reflective LCDdevice such as a liquid crystal on silicon (LCOS), or a digital micromirror device (DMD) may be used, and a light emitting element may beused as a light source. Further, the reflective spatial light modulatingdevice may be configured with an LCD device and a polarization beamsplitter that reflects part of light from the light source to be guidedto the LCD device and transmits part of light reflected by the LCDdevice to be guided to an optical system. As the light emitting elementsconstituting the light source, the red light emitting element, the greenlight emitting element, the blue light emitting element, and the whitelight emitting element may be used, or white light may be obtained bymixing red, green, and blue light output from the red light emittingelement, the green light emitting element, and the blue light emittingelement using the light pipe and performing luminance equalization. Asthe light emitting element, for example, there are examples of asemiconductor laser element, a solid-state laser, and an LED. The numberof pixels may be determined based on specifications necessary for theimage display device, and as a specific value of the number of pixels,there are examples of 320×240, 432×240, 640×480, 1024×768, and1920×1080. Here, in the fourth to sixth forms of image display devices,the light emitting element may be configured with the GaN semiconductorlaser element as described above.

Alternatively, in the image display device of an embodiment of thepresent disclosure having the preferred forms and configurationsdescribed above, the image forming device may be configured to include alight source and a scanning unit that scans parallel light output fromthe light source. Here, a configuration of this image forming device isreferred to as a “second form of image forming device” for convenience.

A light emitting element can be included as a light source in the secondform of image forming device, and specifically include a red lightemitting element, a green light emitting element, a blue light emittingelement, and a white light emitting element. Alternatively, white lightmay be obtained by mixing red, green, and blue light beams output fromthe red light emitting element, the green light emitting element, andthe blue light emitting element using the light pipe and performingluminance equalization. As the light emitting element, for example,there are examples of a semiconductor laser element, a solid-statelaser, and an LED. In the second form of image forming device, thenumber of pixels (virtual pixels) may be determined based onspecifications necessary for the image display device. As a specificvalue of the number of pixels (virtual pixels), there are examples of320×240, 432×240, 640×480, 854×480, 1024×768, and 1920×1080. Inaddition, in the case of a color display, when the light source includesthe red light emitting element, the green light emitting element, andthe blue light emitting element, it is preferable to perform colorsynthesis, for example, using a cross prism. As the scanning unit, forexample, a micro electro mechanical system (MEMS), which has a micromirror rotatable in a 2D direction to horizontally and vertically scanlight output from the light source, or a galvano mirror can be included.It is only necessary to form the relay optical system constituting theparallel light outputting optical system by a well-known relay opticalsystem. Here, in the fourth to sixth forms of image display devices, thelight emitting element may be configured with the GaN semiconductorlaser element as described above.

In the first form of image forming device or the second form of imageforming device, light converted into a plurality of beams of parallellight is incident on the light guide plate through the optical system(that is an optical system that outputs parallel light, which is alsocalled a “parallel light outputting optical system,” and specifically,for example, a collimating optical system or a relay optical system),but the parallel light is necessary because it is necessary to storeoptical wavefront information when the light is incident on the lightguide plate even after the optical wavefront information is output fromthe light guide plate through the first polarizing unit and the secondpolarizing unit. Here, in order to generate a plurality of beams ofparallel light, specifically, for example, it is preferable that a lightoutput portion of an image forming device be positioned at a place (aposition) of a focal distance of the parallel light outputting opticalsystem. The parallel light outputting optical system has a function ofconverting position information of a pixel into angle information in theoptical system of the optical device. As the parallel light outputtingoptical system, there is an example of an optical system having positiveoptical power as a whole in which a convex lens, a concave lens, afree-form surface prism, or a hologram lens is independently arranged orthe lenses are combined. A light shielding portion having an openingportion may be arranged between the parallel light outputting opticalsystem and the light guide plate in order to prevent undesired lightfrom being output from the parallel light outputting optical system andincident on the light guide plate.

For example, the light guide plate can be formed of a glass materialincluding optical glass such as quartz glass or BK7, or a plasticmaterial (e.g., poly methyl methacrylate (PMMA), a polycarbonate resin,an acrylic resin, amorphous polypropylene resin, or a styrene resinincluding acrylonitrile styrene (AS) resin). The shape of the lightguide plate is not limited to a flat plate, but may be curved. As amaterial for forming the light guide plate, a glass including opticalglass such as quartz glass or BK7, or a plastic material (e.g., PMMA, apolycarbonate resin, an acrylic resin, an amorphous polypropylene resin,or a styrene resin including an acrylonitrile styrene (AS) resin) may beused. The shape of the light guide plate is not limited to a flat platebut may be a curved shape.

In the display device of an embodiment of the present disclosure, aframe may be configured with a front portion arranged in front of theobserver and two temple portions rotatably mounted on both ends of thefront portion via a hinge. Here, an ear bend portion is mounted on a tipend portion of each temple portion. The image display device is mountedon the frame, and specifically, for example, the image forming device ispreferably mounted on the temple portion. Further, a configuration inwhich the front portion and the two temple portions are integrated maybe provided. In other words, in view of the entire display device of anembodiment of the present disclosure, the frame has substantially thesame structure as normal glasses. A material for forming the frameincluding a pad portion may be the same material as a material forforming normal glasses such as a metal, an alloy, a plastic, or acombination thereof. Further, a configuration in which a nose pad ismounted on the front portion may be provided. In other words, in view ofthe entire display device of an embodiment of the present disclosure, anassembly of the frame and the nose pad has substantially the samestructure as normal glasses except that there is no rim. The nose padmay also have a known configuration and structure.

From the viewpoint of design or ease of wearing, it is preferable thatwirings (signal lines, power lines, or the like) from one or two imageforming devices be formed to extend from the tip end portion of the earbend portion to the outside via the temple portion and the inside of theear bend portion and to be connected to the control device (a controlcircuit or a control unit). Further, it is preferable to configure aform in which each image forming device includes a headphone unit, and awiring for the headphone unit from each image forming device extendsfrom the tip end portion of the ear bend portion to the headphone unitvia the temple portion and the inside of the ear bend portion. Examplesof the headphone unit are an inner-ear type of headphone unit and acanal type of headphone unit. More specifically, it is preferable toconfigure a form in which the wiring for the headphone unit from the tipend portion of the ear bend portion wraps around the rear side of theauricle (auditory capsule) and extends to the headphone unit.

In addition, in the HMD, an imaging device can be formed to be mountedon a center portion of the front portion. Specifically, the imagingdevice is formed by a solid-state imaging device, for example, formed bya CCD or a CMOS sensor and a lens. It is only necessary that a wiringextending from the imaging device be connected to one image displaydevice (or an image forming device), for example, through the frontportion and further included in a wiring extending from the imagedisplay device (or the image forming device).

Light beams that have been output from the center of the image formingdevice and have passed through the image forming device side node of theoptical system are referred to as “central light beams,” and light beamsthat are vertically incident on the optical device among the centrallight beams are referred to as “central incident light beams.” Further,a point at which the central incident light beams are incident on theoptical device is referred to as an optical device central point, anaxial line that passes through the optical device central point and isparallel to an axial line direction of the optical device is referred toas an X axis, and an axial line that passes through the optical devicecentral point and matches a normal line of the optical device isreferred to as a Y axis. In the display device of an embodiment of thepresent disclosure, the horizontal direction is a direction parallel tothe X axis and is hereinafter also referred to as an “X axis direction.”Here, the optical system is arranged between the image forming deviceand the optical device, and converts light output from the image formingdevice into parallel light. Further, beams converted into parallel lightby the optical system are incident on, guided to, and output to theoptical device. A central point of the first polarizing unit is referredto as an “optical device central point.”

The display device of an embodiment of the present disclosure having thevarious modified examples described above can be used, for example, fora display of various kinds of descriptions, symbols, signs, marks,emblems, or designs when an observation target (subject) such as variouskinds of devices are driven, operated, maintained, disassembled, or thelike, a display of various kinds of descriptions, symbols, signs, marks,emblems, or designs related to an observation target (subject) such as aperson or a product, a display of a moving image or a still image, adisplay of subtitles of a movie or the like, a display of descriptivetext or closed captions related to a video synchronized with a video, ora display of various kinds of descriptions related to an observationtarget (subject) in a drama, kabuki, Noh, a comic drama, an opera, aconcert, a ballet, various kinds of plays, an amusement park, an artgallery, a sightseeing area, a resort, a tourist guide, or the like,descriptive text for describing content or a progress state thereof, abackground, or the like, etc., and can be used for a display of closedcaptions. Here, various kinds of content described above correspond toinformation corresponding to data related to a subject. In a drama,kabuki, Noh, a comic drama, an opera, a concert, a ballet, various kindsof plays, an amusement park, an art gallery, a sightseeing area, aresort, a tourist guide, or the like, it is preferable to display textserving as an image associated with an observation target through thedisplay device at an appropriate timing. Specifically, for example,according to a progress state of a movie or the like or according to aprogress state of a drama, based on a certain schedule or an allocationof time, by an operator's operation or under control of a computer orthe like, an image control signal is transmitted to the display device,and an image is displayed on the display device. Further, a display ofvarious kinds of descriptions related to an observation target (subject)such as various kinds of devices, people, or products is performed, butby shooting an observation target (subject) such as various kinds ofdevices, people, or products and analyzing shot content in the displaydevice, it is possible to display various kinds of previously createddescriptions related to an observation target (subject) such as variouskinds of devices, people, or products through the display device.Alternatively, the display device of an embodiment of the presentdisclosure can be used as a stereoscopic display device. In this case,it is preferable that a polarizing plate or a polarizing film beremovably mounted on the optical device, or a polarizing plate or apolarizing film be attached to the optical device as necessary.

An image signal to be output to the image forming device may include notonly an image signal (for example, text data) but also luminance data(luminance information) related to an image to be displayed,chromaticity data (chromaticity information), or luminance data andchromaticity data. As the luminance data, luminance data correspondingto luminance of a certain region including an observation target viewedthrough the optical device may be used, and as the chromaticity data,chromaticity data corresponding to chromaticity of a certain regionincluding an observation target viewed through the optical device may beused. As described above, it is possible to control luminance(brightness) of an image to be displayed when the luminance data relatedto the image is included, it is possible to control chromaticity (color)of an image to be displayed when the chromaticity data related to theimage is included, and it is possible to control luminance (brightness)and chromaticity (color) of an image to be displayed when the luminancedata and the chromaticity data related to the image are included. Whenluminance data corresponding to luminance of a certain region includingan observation target viewed through the image display device is used,it is preferable to set a value of the luminance data so that a value ofluminance of an image increases (that is, an image is more brightlydisplayed) as a value of the luminance of the certain region includingthe observation target viewed through the image display deviceincreases. Further, when chromaticity data corresponding to chromaticityof a certain region including an observation target viewed through theimage display device is used, it is preferable to set a value of thechromaticity data so that the chromaticity of the certain regionincluding the observation target viewed through the image display deviceand the chromaticity of the image to be displayed roughly have acomplementary color relation. A complementary color refers to acombination of colors having an exactly opposite positional relation ina color circle. For example, a color complementary to red is green, acolor complementary to yellow is purple, and a color complementary toblue is orange. It also refers to a color that causes saturation todecrease, such as white in case of light or black in case of an objectwhen a certain color is mixed with another color at an appropriateratio, but complementarity of a visual effect when arranged in parallelis different from complementarity when mixed. It is also referred to asa contrast color and an opposite color. Here, an opposite color refersto a color directly opposite to a complementary color, whereas a rangeindicated by a complementary color is slightly larger. A colorcombination of complementary colors creates a synergy effect in whichboth colors are emphasized, which is referred to as complementary colorharmony.

Embodiment 1

Embodiment 1 relates to a display device (specifically, an HMD) and animage display device of an embodiment of the present disclosure, andmore particularly, to the first and third forms of image displaydevices). FIG. 1 is a conceptual diagram of an image display device in adisplay device of Embodiment 1, FIG. 2 is a schematic top view of thedisplay device of Embodiment 1, FIG. 3 is a schematic front viewillustrating the display device of Embodiment 1, and FIG. 4 is aschematic side view illustrating the display device of Embodiment 1.FIG. 5 schematically illustrates propagation of light in a light guideplate constituting an image display device.

The display device of Embodiment 1 and Embodiments 2 to 11 to bedescribed later is more specifically an HMD, and includes

(I) a frame (for example, the glasses-type frame 10) mounted on a headof an observer, and

(II) image display devices 100, 200, 300, 400, 500, and 800 attached tothe frame 10.

Here, the display device of Embodiment 1 or the display devices ofEmbodiments 2 to 11 to be described later is specifically a binoculardisplay device including two image display devices or may be a monoculardisplay device including one image display device. For example, imageforming devices 111 and 211 display a single-color (for example, green)image.

In Embodiment 1 or Embodiments 2 to 11 to be described later, the imagedisplay devices 100, 200, 300, 400, 500, and 800 include

(A) the image forming devices 111 and 211,

(B) optical devices (light guide devices)120, 320, 520, and 820 on whichlight output from the image forming devices 111 and 211 is incident andfrom which the light is output,

(C) light receiving devices 126, 326, 127, 327, 128, 328, and 825 thatdetect light output from the image forming devices 111 and 211, and

(D) optical systems (parallel light outputting optical systems) 112 and254 that convert light output from the image forming devices 111 and 211into parallel light, and

beams converted into the parallel light through the optical systems 112and 254 are incident on and output to optical devices 120, 320, 520, and820.

Here, the image display devices 100, 200, 300, 400, 500, and 800 may bemounted to be fixed to the frame or may be removably mounted. Here, theoptical systems 112 and 254 are arranged between the image formingdevices 111 and 211 and the optical devices 120, 320, 520, and 820. Thebeams converted into the parallel light through the optical systems 112and 254 are incident on and output to the optical devices 120, 320, 520,and 820. The optical devices 120, 320, 520, and 820 are of asemi-transmissive type (see-through type). Specifically, at least aportion (more specifically, light guide plates 121, 321, and 821 andsecond polarizing units 140 and 340 or a semi-transmissive mirror 822which will be described later) of an optical device facing both eyes ofthe observer are semi-transmissive (see-through).

In Embodiment 1 and Embodiments 2 to 9 to be described later, a point atwhich central incident light beams vertically incident on the opticaldevices 120 and 320 among light beams (central light beams CL) that areoutput from the centers of the image forming devices 111 and 211 andpass through image forming device side nodes of the optical systems 112and 254 are incident on the optical devices 120 and 320 is referred toas an optical device central point O, an axial line that passes throughthe optical device central point O and is parallel to axial linedirections of the optical devices 120 and 320 is referred to as an Xaxis, and an axial line that passes through the optical device centralpoint O and matches normal lines of the optical devices 120 and 320 isreferred to as a Y axis. Here, central points of the first polarizingunits 130 and 330 are the optical device central point O. In otherwords, as illustrated in FIG. 5, in the image display devices 100, 200,300, and 400, the central incident light beams CL that are output fromthe centers of the image forming devices 111 and 211 and pass throughthe image forming device side nodes of the optical systems 112 and 254collide vertically with the light guide plates 121 and 321. In otherwords, the central incident light beams CL are incident on the lightguide plates 121 and 321 at an incidence angle of 0°. In this case, thecenter of an image to be displayed matches vertical directions of firstsurfaces 122 and 322 of the light guide plates 121 and 321.

The optical devices 120 and 320 in Embodiment 1 and Embodiments 2 to 9to be described later include

(a) the light guide plates 121 and 321 that cause the incident light topropagate inside the light guide plate according to total reflection andthen output the incident light,

(b) the first polarizing units 130 and 330 that polarize the lightincident on the light guide plates 121 and 321 so that the lightincident on the light guide plates 121 and 321 is totally reflectedinside the light guide plates 121 and 321, and

(c) the second polarizing units 140 and 340 that polarize lightpropagating inside the light guide plates 121 and 321 according to totalreflection so that part of light propagating inside the light guideplates 121 and 321 according to total reflection is output from thelight guide plates 121 and 321.

Here, the second polarizing units 140 and 340 are formed of a reflectivevolume hologram diffraction grating. In other words, the secondpolarizing units 140 and 340 functions as a semi-transmissive mirror.

In Embodiment 1 or Embodiments 2 to 5 to be described later, the opticaldevices 120 and 320 include the first form of image display device.Specifically, the second polarizing units 140 and 340 include

first portions 141 and 341 that polarize light propagating inside thelight guide plates 121 and 321 according to total reflection toward theobserver, and

second portions 142 and 342 that polarize the light propagating insidethe light guide plates 121 and 321 according to total reflection towardthe light receiving devices 126 and 326.

Alternatively, in the image display devices 100, 200, 300, and 400 ofEmbodiment 1 and Embodiments 2 to 5 to be described later, the opticaldevices 120 and 320 include a light semi-reflecting member that reflectpart of light output from the image forming devices 111 and 211 andtransmit the remaining part, and the light receiving devices 126 and 326detect the light passing through the light semi-reflecting member. Here,specifically, the light semi-reflecting member is formed of the secondpolarizing units 140 and 340.

In Embodiment 1 and Embodiments 2 to 11 to be described later, the lightreceiving devices 126, 326, 127, 327, 128, 328, and 825 include aso-called line sensor in which light receiving elements areone-dimensionally arranged or a so-called imaging element in which lightreceiving elements are arranged in a 2D matrix.

Alternatively, in Embodiment 1 and Embodiments 2 to 11 to be describedlater, the light receiving devices 126, 326, 127, 327, 128, 328, and 825are optically connected to the optical devices 120, 320, 520, and 820.In other words, the light receiving devices 126, 326, 127, 327, 128,328, and 825 employ not only a form in which the light receiving devices126, 326, 127, 327, 128, 328 are connected directly to the opticaldevices 120, 320, 520, and 820 but also a form in which the lightreceiving devices 126, 326, 127, 327, 128, 328 are connected so thatlight is input via an adhesive member, a light guide member, or thelike. Further, as light detected by the light receiving devices 126,326, 127, 327, 128, 328, and 825, part of light output from the imageforming devices 111 and 211 or part of light propagating through theoptical devices 120, 320, 520, and 820 is sufficient.

In Embodiment 1, the first polarizing unit 130 and the second polarizingunit 140 are disposed inside the light guide plate 121. The firstpolarizing unit 130 reflects light incident on the light guide plate121, and the second polarizing unit 140 transmits and reflects lightpropagating through the inside of the light guide plate 121 according tototal reflection a plurality of times. That is, the first polarizingunit 130 functions as a reflecting mirror, and the second polarizingunit 140 functions as a semi-transmissive mirror. More specifically, thefirst polarizing unit 130 provided inside the light guide plate 121includes a light reflecting film (a type of mirror) formed of aluminum(Al), which reflects light incident on the light guide plate 121. On theother hand, the second polarizing unit 140 provided inside the lightguide plate 121 is formed by a multilayer laminated structure in which aplurality of dielectric laminated films are laminated. The dielectriclaminated film is formed by, for example, a TiO₂ film as ahigh-dielectric-constant material and a SiO₂ film as alow-dielectric-constant material. A multi-layer laminated structure inwhich a plurality of dielectric laminated films are laminated isdisclosed in Japanese Unexamined Patent Application Publication(Translation of PCT Application) 2005-521099. Although a six-layerdielectric laminated film is illustrated in the drawing, the presentdisclosure is not limited thereto. A thin section formed of the samematerial as the material constituting the light guide plate 121 issandwiched between dielectric laminated films. In the first polarizingunit 130, the parallel light incident on the light guide plate 121 isreflected (or diffracted) so that the parallel light incident on thelight guide plate 121 is totally reflected inside the light guide plate121. On the other hand, in the second polarizing unit 140, the parallellight propagating through the inside of the light guide plate 121according to total reflection is reflected (or diffracted) a pluralityof times, and output toward the pupil 21 of the observer in a state ofparallel light from the light guide plate 121.

For the first polarizing unit 130, it is only necessary that a slantsurface on which the first polarizing unit 130 is to be formed on thelight guide plate 121 be provided by cutting out a portion 124 on whichthe first polarizing unit 130 of the light guide plate 121 is provided,and the cut-out portion 124 of the light guide plate 121 be adhered tothe first polarizing unit 130 after a light reflecting film is vacuumevaporated on the slant surface. In addition, for the second polarizingunit 140, it is only necessary that a multilayer laminated structure inwhich a plurality of membranes of the same material (e.g., glass) as thematerial constituting the light guide plate 121 and a plurality ofdielectric laminated films (for example, formable by vacuum evaporation)are laminated be manufactured, a slant surface be formed by cutting outa portion 125 on which the second polarizing unit 140 of the light guideplate 121 is provided, the multilayer laminated structure be adhered tothe slant surface, and the external form be arranged by polishing or thelike. Thereby, the optical device 120 having the first polarizing unit130 and the second polarizing unit 140 provided inside the light guideplate 121 can be obtained. Here, the first polarizing unit 130 may beconfigured with a semi-transmissive mirror that reflects part of lightincident on the light guide plates 121 and 321. In the second polarizingunit 140, the dielectric laminated film 140A positioned on the endportion side of the light guide plate 121 at the second polarizing unitside may be replaced with a light reflecting film.

Here, in Embodiment 1 or any one of Embodiments 2 to 10 to be describedlater, the light guide plates 121 and 321, and 821 are formed of anoptical glass material or a plastic material. Further, in Embodiment 1or any one of Embodiments 2 to 9 to be described later, the light guideplate 121 or 321 has two parallel surfaces (a first surface 122 or 322and a second surface 123 or 323) extending in parallel to the lightpropagating direction (X direction) according to internal totalreflection of the light guide plate 121 or 321. The first surface 122 or322 and the second surface 123 or 323 face each other. Parallel light isincident from the first surface 122 or 322 corresponding to a lightincidence surface, and the incident parallel light propagates throughthe inside according to total reflection and then is output from thefirst surface 122 or 322 corresponding to a light output surface.However, the present disclosure is not limited thereto, and the lightincidence surface may be formed by the second surface 123 or 323, andthe light output surface may be formed by the first surface 122 or 322.In Embodiment 1, the light receiving device 126 is mounted on the lightoutput surface.

In Embodiment 1 or 4 to be described later, the image forming device 111is the first form of image forming device, which has a plurality ofpixels arranged in a 2D matrix. Specifically, the image forming device111 includes a reflective spatial light modulating device 150 and alight source 153 formed by LEDs that emits white light. Each entireimage forming device 111 is fitted inside a housing 113 (denoted by adashed-dotted line in FIG. 1), and an opening portion (not illustrated)is provided in the housing 113, and light is output from the opticalsystem (the parallel light outputting optical system, the collimatingoptical system) 112 through the opening portion. The reflective spatiallight modulating device 150 is formed by an LCD device (LCD) 151 formedby an LCOS as a light valve and a polarization beam splitter 152 thatreflects part of the light output from the light source 153 to guide thereflected light to the LCD device 151 and passes part of light reflectedby the LCD device 151 to guide the passed light to the optical system112. The liquid crystal display device 151 includes a plurality (forexample, 640×480) of pixels (liquid crystal cells) arranged in a 2Dmatrix. The polarization beam splitter 152 has a well-knownconfiguration and structure. Unpolarized light output from the lightsource 153 collides with the polarization beam splitter 152. Thepolarization beam splitter 152 passes and outputs a P-polarizedcomponent outside the system. On the other hand, an S-polarizedcomponent is reflected by the polarization beam splitter 152, incidenton the LCD device 151, reflected inside the LCD device 151, and outputfrom the LCD device 151. Here, a large number of P-polarized componentsare included in light output from pixels used for displaying “white” inthe light output from the LCD device 151, and a large number ofS-polarized components are included in light output from pixels used fordisplaying “black.” Accordingly, the P-polarized component within thelight that is output from the LCD device 151 and collides with thepolarization beam splitter 152 passes through the polarization beamsplitter 152 and is guided to the optical system 112. On the other hand,the S-polarized component is reflected by the polarization beam splitter152 and returned to the light source 153. The optical system 112, forexample, includes a convex lens. To generate parallel light, the imageforming device 111 (more specifically, the LCD device 151) is disposedat a place (position) of a focal distance of the optical system 112.

The frame 10 is formed by a front portion 11 arranged on the front sideof the observer, two temple portions 13 pivotably mounted on both endsof the front portion 11 via hinges 12, and ear bend portions (alsoreferred to as tip cells or ear pads) 14 mounted on tip end portions ofthe temple portions 13. In addition, nose pads (not illustrated) aremounted thereon. That is, the assembly of the frame 10 and the nose padshas basically substantially the same structure as ordinary glasses.Further, each housing 113 is mounted attachable to or detachable fromthe temple portion 13 using a mounting member 19. The frame 10 ismanufactured using metal or plastic. Each housing 113 may be fixed onthe temple portion 13 using the mounting member 19 so as not to beattachable to or detachable from the temple portion 13. Further, whenthe observer owns and wears glasses, each housing 113 may be attachableto or detachable from the temple portion of the frame of the glassesowned by the observer using the mounting member 19.

Further, wirings (signal lines, power lines, and the like) 15 extendingfrom one image forming device 111A extend from the tip end portion ofthe ear bend portion 14 toward the outside via the temple portion 13 andthe inside of the ear bend portion 14, and are connected to the controldevice (the control circuit or the control unit) 18. In addition, eachof the image forming devices 111A and 111B has a headphone unit 16, anda headphone wiring 16′ extending from each of the image forming devices111A and 111B extends from the tip end portion of the ear bend portion14 to the headphone unit 16 via the temple portion 13 and the inside ofthe ear bend portion 14. More specifically, the headphone wiring 16′extends from the tip end portion of the ear bend portion 14 so as towrap around the rear side of the auricle (auditory capsule) and extendsto the headphone unit 16. According to such a configuration, the displaydevice can be neatly formed without giving an impression that theheadphone unit 16 and the headphone wiring 16′ are cluttered.

The wirings (signal lines, power lines, and the like) 15 are connectedwith the control device (control circuit) 18 as described above. In thecontrol device 18, processing for image display is performed. Thecontrol device 18 may be configured with a known circuit.

In addition, an imaging device 17 having a solid-state imaging deviceformed by a CCD or CMOS sensor and a lens (these are not illustrated)are mounted on a center portion 11′ of the front portion 11 using anappropriate mounting member (not illustrated). A signal output from theimaging device 17 is transmitted to the image forming device 111A via awiring (not illustrated) extending from the imaging device 17.

In the image display devices 100, 200, 300, 400, 500, and 800 ofEmbodiment 1 and Embodiments 2 to 11 to be described later, in order todetect the occurrence of an abnormality, preferably, a test signal istransmitted to the image forming devices 111 and 211, for example,during one image display frame at intervals of a certain period of time(for example, at intervals of 10 seconds or 1 minute), a test pattern isdisplayed on the image forming devices 111 and 211, and the relevanttest pattern is detected by the light receiving devices 126, 326, 127,327, 128, 328, and 825. Alternatively, preferably, when the operationsof the image display devices 100, 200, 300, 400, 500, and 800 start orend, the test signal is transmitted to the image forming devices 111 and211, the test pattern is displayed on the image forming devices 111 and211, and the relevant test pattern is detected by the light receivingdevices 126, 326, 127, 327, 128, 328, and 825. When the image displaydevices 100, 200, 300, 400, 500, and 800 operate normally, the testpattern is received in certain pixels of the light receiving devices126, 326, 127, 327, 128, 328, and 825. However, when an abnormalityoccurs in the image display devices 100, 200, 300, 400, 500, and 800,the test pattern is received in pixels deviated from certain pixels ofthe light receiving devices 126, 326, 127, 327, 128, 328, and 825.Alternatively, when an abnormality occurs in the image display devices100, 200, 300, 400, 500, and 800, there are also cases in whichintensity of light received by the light receiving devices 126, 326,127, 327, 128, 328, and 825 is reduced. Thus, when the light receivingdevices 126, 326, 127, 327, 128, 328, and 825 detect the occurrence ofthe abnormality in the image display devices 100, 200, 300, 400, 500,and 800, the image display devices 100, 200, 300, 400, 500, and 800 orthe display device output a warning.

Alternatively, in the image display devices 100, 200, 300, 400, 500, and800 of Embodiment 1 and Embodiments 2 to 11 to be described later, theoperations of the image forming devices 111 and 211 are controlled basedon the detection results of the light receiving devices 126, 326, 127,327, 128, 328, and 825. In other words, the positions of images outputfrom the image forming devices 111 and 211 are controlled based on thedetection results of the light receiving devices 126, 326, 127, 327,128, 328, and 825. Specifically, when the test pattern is received inthe pixels deviated from the certain pixels of the light receivingdevices 126, 326, 127, 327, 128, 328, and 825, preferably, image signalsto be output to the image forming devices 111 and 211 are compensated toeliminate the deviation. More specifically, for movement of an image inthe horizontal direction, it is preferable that a signal in which aposition of an image in the horizontal direction is changed by +i pixelsor −i pixels be generated in the control device 18 as a display positioncorrection signal. Alternatively, it is preferable that a signal inwhich a timing of a horizontal synchronous signal is changed by +ipixels or −i pixels be generated in the control device 18. Further, formovement of an image in the vertical direction, it is preferable that asignal in which a position of an image in the vertical direction ischanged by +j pixels or −j pixels be generated in the control device 18as the display position correction signal, and alternatively, it ispreferable that a signal in which a timing of a vertical synchronoussignal is changed by +j pixels or −j pixels be generated in the controldevice 18. In other words, it can be implemented by delaying oradvancing a timing for a memory read position of the image, or it can beimplemented by deviating timings of the vertical synchronous signal andthe horizontal synchronous signal. Further, it is preferable that thedisplay position correction signal be stored in the control device 18 asthe display position control signal, and it is preferable that thedisplay position control signal be added to the image signal for formingthe image in the control device 18. Alternatively, an output angle oflight output from the optical devices 120 and 320 may be controlled, andin order to compensate for distortion occurring in the images outputfrom the image forming devices 111 and 211, signals for compensating fordistortion occurring in the images may be weighted to the image signalsto be output to the image forming devices 111 and 211 to remove thedistortion. In other words, the signals for compensating for distortionoccurring in the images output from the optical devices 120, 320, 520,and 820 may be output to the image forming devices 111 and 211 based onthe detection results of the light receiving devices 126, 326, 127, 327,128, 328, and 825.

Alternatively, when intensity of light received by the light receivingdevices 126, 326, 127, 327, 128, 328, and 825 is reduced, it ispreferable to perform processing (for example, an increase in lightintensity of the light source 153) of increasing light intensity of theimages formed in the image forming devices 111 and 211.

As described above, the image display device or the display device ofEmbodiment 1 includes the light receiving device that detects lightoutput from the image forming device, and thus it is possible toimmediately detect whether or not an image to be displayed on an imagedisplay device or light output from an optical device is abnormal with ahigh degree of accuracy.

Embodiment 2

Embodiment 2 is a modification of Embodiment 1 and relates to fourth andsixth forms of image display devices. In Embodiment 2, the image formingdevice 111 includes the light source 153 formed of a GaN semiconductorlaser element. Further, the wavelength of light output from the lightsource 153 is controlled based on the detection result of the lightreceiving device 126.

Generally, an oscillation wavelength (a wavelength λ output from asemiconductor laser element) of a semiconductor laser element is shiftedto a long wavelength side with an increase in the temperature of abonded surface. When the wavelength λ output from the semiconductorlaser element is shifted to the long wavelength side, as will bedescribed later, the deviation from the Bragg condition represented byExpression (A) occurs, and thus the image quality of the image observedby the observer is lowered. However, in a GaN semiconductor laserelement formed by laminating a GaN compound semiconductor layer, anoscillation wavelength (the wavelength λ output from the semiconductorlaser element) of the semiconductor laser element is shifted to a shortwavelength side with an increase in a driving current. Thus, it ispossible to compensate the oscillation wavelength of the semiconductorlaser element shifted to the long wavelength side with the increase inthe temperature. In other words, in order to detect whether or not thewavelength of light output from the light source 153 has significantlychanged, the test signal is transmitted to the image forming device 111during one image display frame at intervals of a certain period of time(for example, at intervals of 10 seconds or 1 minute), the test patternis displayed on the image forming device 111, and the relevant testpattern is detected by the light receiving device 126. When thewavelength of light output from the light source 153 does notsignificantly change, since the deviation from the Bragg condition doesnot occur, the test pattern is received in a certain pixel of the lightreceiving device 126. However, when the wavelength of light output fromthe light source significantly changes, specifically, when thewavelength of light output from the light source increases due to heatgeneration of the light source, the diffraction angle changes, and thusthe test pattern is received in a pixel deviated from the certain pixelof the light receiving device 126. Alternatively, there are also casesin which intensity of light received by the light receiving device 126is reduced. Such a phenomenon causes an image observed by the observerto be smeared or distorted. Thus, when such a phenomenon is detected bythe light receiving device 126, it is preferable that the wavelength oflight output from the light source 153 be shifted to the shortwavelength side to return to the original wavelength by increasing thedriving current of the GaN semiconductor laser element constituting thelight source 153 under control of the control device 18. Here, thetemperature of the light source 153 may be measured in conjunction withthe detection of the test pattern by the light receiving device 126.

Because the image display device and the display device of Embodiment 2have substantially the same configuration and structure as the imagedisplay device and the display device of Embodiment 1 except for theabove-described points, a detailed description thereof is omitted.

Embodiment 3

Embodiment 3 is a modification of Embodiment 1 or Embodiment 2. Asillustrated in FIG. 6 that is a conceptual diagram of the image displaydevice 200 in the display device (head mounted display) of Embodiment 3,in Embodiment 3, the image forming device 211 is configured with thesecond form of image forming device. In other words, a light source 251and a scanning unit 253 that scans parallel light output from the lightsource 251 are provided. More specifically, the image forming device 211includes

(I) the light source 251,

(II) a collimating optical system 252 that converts light output fromthe light source 251 into parallel light,

(III) the scanning unit 253 that scans the parallel light output fromthe collimating optical system 252, and

(IV) the relay optical system 254 that relays and outputs the parallellight scanned by the scanning unit 253.

The whole image forming device 211 is received in a housing 213(indicated by an alternate long and short dash line in FIG. 6), anopening portion (not illustrated) is formed in the housing 213, andlight is output from the relay optical system 254 through the openingportion. Each housing 213 is removably mounted on the temple portion 13through the mounting member 19.

The light source 251 is configured with a light emitting element thatemits white light. Alternatively, the light source 251 is formed of aGaN semiconductor laser element. Light output from the light source 251has positive optical power as a whole and is incident on the collimatingoptical system 252 and output as parallel light. Then, the parallellight is reflected by the total reflecting mirror 256, scannedhorizontally and vertically by the scanning unit 253 including an MEMSthat has a micro mirror rotatable in a 2D direction to scan incidentparallel light two dimensionally, and converted into a type of 2D image,and virtual pixels (for example, the number of pixels may be the same asin Embodiment 1) are generated. Then, light from the virtual pixelspasses through the relay optical system (the parallel light outputtingoptical system) 254 configured with a known relay optical system, andparallel light beams are incident on the optical device 120.

The optical device 120, which the parallel light beams formed by therelay optical system 254 are incident on, guided to, and output to, hassubstantially the same configuration and structure as the optical devicedescribed in Embodiment 1 or Embodiment 2, and thus a detaileddescription thereof is omitted. The display device of Embodiment 3 hassubstantially the same configuration and structure as the display deviceof Embodiment 1 or Embodiment 2 except for the difference in the imageforming device 211, and thus a detailed description thereof is omitted.

Embodiment 4

Embodiment 4 is a modification of Embodiment 1 or Embodiment 2. Aconceptual diagram of an image display device of a display device (headmounted display) of Embodiment 4 is illustrated in FIG. 7. A schematiccross-sectional view in which a part of the reflective volume hologramdiffraction gratings is enlarged is illustrated in FIG. 8. In Embodiment4, the image forming device 111 is configured with the first form ofimage forming device, similarly to Embodiment 1 and Embodiment 2. Theoptical device 320 is the same basic configuration and structure as theoptical device 120 of Embodiment 1 or Embodiment 2 except for thedifference in the configuration and structure of the first polarizingunit and the second polarizing unit.

In Embodiment 4, the first polarizing unit and the second polarizingunit are disposed on a surface of a light guide plate 321 (specifically,a second surface 323 of the light guide plate 321). The first polarizingunit diffracts light incident on the light guide plate 321, and thesecond polarizing unit diffracts light propagating through the inside ofthe light guide plate 321 according to total reflection a plurality oftimes. Here, the first polarizing unit and the second polarizing unitare formed by diffraction grating elements, specifically, reflectivediffraction grating elements, and more specifically, reflective volumehologram diffraction gratings. In the following description, the firstpolarizing unit formed by the reflective volume hologram diffractiongrating is referred to as a “first diffraction grating member 330” forconvenience, and the second polarizing unit formed by the reflectivevolume hologram diffraction grating is referred to as a “seconddiffraction grating member 340” for convenience.

In Embodiment 4 or Embodiment 5 to be described later, the firstdiffraction grating member 330 and the second diffraction grating member340 can be formed by laminating one diffraction grating layer. In eachdiffraction grating layer formed by a photopolymer material,interference fringes corresponding to one type of wavelength band (orwavelength) are formed, and manufactured using a method of the relatedart. The pitch of the interference fringes formed in the diffractiongrating layer (diffractive optical element) is constant, and theinterference fringes have a linear shape and is in parallel to the Zaxis. The axial lines of the first diffraction grating member 330 andthe second diffraction grating member 340 are parallel to the X axis,and the normal lines thereof are parallel to the Y axis.

A schematic partial cross-sectional view in which the reflective volumehologram diffraction grating is enlarged is illustrated in FIG. 8. Inthe reflective volume hologram diffraction grating, interference fringeshaving a slant angle ϕ are formed. Here, the slant angle ϕ represents anangle formed by the surface of the reflective volume hologramdiffraction grating and the interference fringes. The interferencefringes are formed from the inside of the reflective volume hologramdiffraction grating to the surface thereof. The interference fringessatisfy a Bragg condition. Here, the Bragg condition is a condition thatsatisfies the following Expression (A). In Expression (A), m representsa positive integer, λ represents a wavelength, d represents the pitch ofthe grating surface (a gap of virtual planes including the interferencefringes in the direction of the normal line), and Θ represents acomplementary angle of an angle at which light is incident on theinterference fringes. In addition, when light penetrates into thediffraction grating member at an incidence angle ψ, the relationshipamong the complementary angle Θ, the slant angle ϕ, and the incidenceangle ψ is shown in Expression (B).m·λ=2·d·sin(Θ)  (A)Θ=90°−(ϕ+ψ)  (B)

As described above, the first diffraction grating member 330 is arrangedon (adhered to) the second surface 323 of the light guide plate 321 anddiffracts and reflects parallel light incident on the light guide plate321 so that the parallel light incident from the first surface 322 tothe light guide plate 321 is totally reflected inside the light guideplate 321. Further, as described above, the second diffraction gratingmember 340 is arranged on (adhered to) the second surface 323 of thelight guide plate 321 and diffracts and reflects the parallel lightpropagating through the inside of the light guide plate 321 according tototal reflection a plurality of times, and the parallel light isdirectly output from the first surface 322 of the light guide plate 321.

Then, the parallel light propagates through the inside of the lightguide plate 321 according to total reflection and then is outputtherefrom. At this time, because the light guide plate 321 is thin, anda path of light that propagates through the inside of the light guideplate 321 is long, the number of total reflections until the parallellight reaches the second diffraction grating member 340 differsaccording to a view angle. In further detail, the number of reflectionsof parallel light incident at an angle in a direction close to thesecond diffraction grating member 340 among parallel light beamsincident on the light guide plate 321 is less than that of parallellight incident on the light guide plate 321 at an angle in a directionaway from the second diffraction grating member 340. This is becauseparallel light incident on the light guide plate 321 at an angle closeto the second diffraction grating member 340 among parallel light beamsdiffracted and reflected in the first diffraction grating member 330 hasa smaller angle formed with the normal line of the light guide plate 321when light propagating through the inside of the light guide plate 321collides with the inner surface of the light guide plate 321 thanparallel light incident on the light guide plate 321 at an angle in adirection reverse thereto. In addition, the shape of the interferencefringes formed inside the second diffraction grating member 340 and theshape of the interference fringes formed inside the first diffractiongrating member 330 are symmetrical with respect to the virtual planevertical to the axis of the light guide plate 321.

A light guide plate 321 in accordance with Embodiment 5 to be describedlater also basically has the same configuration and structure as thelight guide plate 321 described above.

The image display device and the display device of Embodiment 4 havesubstantially the same configuration and structure as the image displaydevice and the display device of Embodiment 1 or Embodiment 2 except forthe difference in the optical device 320, and thus a detaileddescription thereof is omitted.

Embodiment 5

Embodiment 5 is a modification of Embodiment 4. FIG. 9 is a conceptualdiagram of an image display device in a display device (head mounteddisplay) of Embodiment 5. In the image display device 400 of Embodiment5, the light source 251, the collimating optical system 252, thescanning unit 253, the parallel light outputting optical system (therelay optical system 254), and the like have substantially the sameconfiguration and structure (the second form of image forming device) asin Embodiment 3. Further, the optical device 320 of Embodiment 5 hassubstantially the same configuration and structure as the optical device320 of Embodiment 4. The display device of Embodiment 5 hassubstantially the same configuration and structure as the display deviceof Embodiment 3 except for the difference described above, and thus adetailed description thereof is omitted.

Embodiment 6

Embodiment 6 is a modification of Embodiment 1 and Embodiments 3 to 5,and relates to the second and third forms of image display devices. Aconceptual diagram of an image display device (an image display deviceaccording to a modified example of Embodiment 1) in a display device ofEmbodiment 6 is illustrated in FIG. 10, a conceptual diagram of anotherimage display device (an image display device according to a modifiedexample of Embodiment 4) in a display device of Embodiment 6 isillustrated in FIG. 11, and similarly to those of Embodiment 1 andEmbodiments 3 to 5, the optical devices 120 and 320 of Embodiment 6include

(a) the light guide plates 121 and 321 that cause the incident light topropagate inside the light guide plates according to total reflectionand then output the incident light,

(b) the first polarizing units 130 and 330 that polarize the lightincident on the light guide plates 121 and 321 so that the lightincident on the light guide plates 121 and 321 is totally reflectedinside the light guide plates 121 and 321, and

(c) the second polarizing units 140 and 340 that polarize lightpropagating inside the light guide plates 121 and 321 according to totalreflection so that part of light propagating inside the light guideplates 121 and 321 according to total reflection is output from thelight guide plates 121 and 321.

The light receiving devices 127 and 327 are arranged at the end portionsof the light guide plates 121 and 321 at the second polarizing units 140and 340 side. Here, all light incident on the second polarizing units140 and 340 is not necessarily output toward the observer, and part oflight incident on the second polarizing units 140 and 340 finally passesthrough the second polarizing units 140 and 340 and reaches the lightreceiving devices 127 and 327.

Alternatively, in the image display devices 100, 200, 300, and 400 ofEmbodiment 6, the optical devices 120 and 320 include a lightsemi-reflecting member that reflects part of light output from the imageforming devices 111 and 211 and transmits the remaining part, and thelight receiving devices 127 and 327 detect the light passing through thelight semi-reflecting member. Here, specifically, the lightsemi-reflecting member is formed of the second polarizing units 140 and340.

The image display device and the display device of Embodiment 6 havesubstantially the same configuration and structure as the image displaydevice and the display device of Embodiment 1 and Embodiments 3 to 5except that arrangement positions of the light receiving devices 127 and327 are different as described above, and thus a detailed descriptionthereof is omitted.

Embodiment 7

Embodiment 7 is a modification of Embodiment 6, and relates to fifth andsixth forms of image display devices. In Embodiment 7, the image formingdevices 111 and 211 include the light sources 153 and 251 formed of aGaN semiconductor laser element. Further, similarly to Embodiment 2, thewavelength of light output from the light sources 153 and 251 iscontrolled based on the detection results of the light receiving devices127 and 327.

The image display device and the display device of Embodiment 7 havesubstantially the same configuration and structure as the image displaydevice and the display device of Embodiment 6 except for theabove-described points, and thus a detailed description thereof isomitted.

Embodiment 8

Embodiment 8 is also a modification of Embodiment 1 and Embodiments 3 to5, and relates to the third form of image display device. A conceptualdiagram of an image display device (an image display device according toa modified example of Embodiment 1) in a display device of Embodiment 8is illustrated in FIG. 12, a conceptual diagram of another image displaydevice (a image display device according to a modified example ofEmbodiment 4) in a display device of Embodiment 8 is illustrated in FIG.13, and as illustrated in FIGS. 12 and 13, the optical devices 120 and320 of Embodiment 8 include a light semi-reflecting member that reflectspart of light output from the image forming devices 111 and 211 andtransmits the remaining part, and the light receiving devices 128 and328 detect the light passing through the light semi-reflecting member.Here, in Embodiment 8, the light semi-reflecting member is configuredwith the first polarizing unit 131, and the first polarizing unit 131 isconfigured with a semi-transmissive mirror that reflects part of lightincident on the light guide plate 121. Alternatively, the lightsemi-reflecting member is configured with the first polarizing unit 330formed of a reflective volume hologram diffraction grating functioningas a semi-transmissive mirror, similarly to Embodiment 4. The lightreceiving device 328 is mounted on a base 329 configured with atransparent member mounted on the light guide plate 321. The secondpolarizing units 140 and 340 transmit and reflect light propagatinginside the light guide plates 121 and 321 according to total reflectiona plurality of times, similarly to Embodiment 1 and Embodiments 3 to 5.

The image display device and the display device of Embodiment 8 havesubstantially the same configuration and structure as the image displaydevices and the display devices of Embodiment 1 and Embodiments 3 to 5except that arrangement positions of the light receiving devices 128 and328 are different and the first polarizing unit 131 is different asdescribed above, and thus a detailed description thereof is omitted.

Embodiment 9

Embodiment 9 is a modification of Embodiment 8, and relates to the sixthform of image display device. In Embodiment 9, the image forming devices111 and 211 include the light sources 153 and 251 formed of a GaNsemiconductor laser element. Further, the wavelength of light outputfrom the light sources 153 and 251 is controlled based on the detectionresults of the light receiving devices 128 and 328, similarly toEmbodiment 2.

The image display device and the display device of Embodiment 9 havesubstantially the same configuration and structure as the image displaydevice and the display device of Embodiment 8 except for theabove-described points, and thus a detailed description thereof isomitted.

Embodiment 10

Embodiment 10 is a modification of the image display devices and theoptical devices of the display device of Embodiments 1 to 9. FIG. 14 isa schematic diagram illustrating a part of the optical device 820 of thedisplay device of Embodiment 10. The image display device 800 ofEmbodiment 10 is the third and sixth forms of image display devices.

In Embodiment 10, the light semi-reflecting member constituting theoptical device 820 is configured with a concave mirror 824 that reflectslight from the image forming devices 111 and 211. The optical device 820further includes the semi-transmissive mirror 822 that outputs lightreflected by the concave mirror 824 toward the observer and a quarterwavelength plate 823 that is arranged between the semi-transmissivemirror 822 and the concave mirror 824. The two semi-transmissive mirrors822 are disposed inside the light guide plate 821. Here, the number ofsemi-transmissive mirrors 822 is not limited to “2,” and, for example,may be “1.” The light from the image forming devices 111 and 211 isincident from one end of the light guide plate 821. The quarterwavelength plate 823 and the concave mirror 824 are arranged on theother end of the light guide plate 821. The concave mirror 824 isconfigured to transmit part of light incident on the concave mirror 824,and the light receiving device 825 is arranged to receive the lightpassing through the concave mirror 824.

The image display device and the display device of Embodiment 10 havesubstantially the same configuration and structure as the image displaydevice and the display device of Embodiments 1 to 9 except for theabove-described points, and thus a detailed description thereof isomitted. Here, the concave mirror 824, the semi-transmissive mirror 822,and the quarter wavelength plate 823 may be supported by an appropriatesupport member, and the light guide plate 821 may be omitted. Further, aconfiguration in which the light from the image forming devices 111 and211 arrives at the concave mirror 824 through the first polarizing units130 and 330 may be provided, and a configuration in which the light fromthe image forming devices 111 and 211 arrives at the concave mirror 824directly may be provided.

Embodiment 11

Embodiment 11 is also a modification of the image display device and theoptical device of the display device of Embodiments 1 to 9. FIG. 15 is aschematic front view of a display device of Embodiment 11, and FIG. 16is a schematic top view of the display device of Embodiment 11.

In Embodiment 11, the optical device 520 constituting the image displaydevice 500 is configured with a semi-transmissive mirror on which lightoutput from the image forming devices 111A and 111B is incident and fromwhich the incident light is output toward a pupil 21 of the observer.The second polarizing units 140 and 340 are arranged in the opticaldevice 520. Here, in Embodiment 11, a structure in which the lightoutput from the image forming devices 111A and 111B propagates insidethe transparent member 521 such as a glass plate or a plastic plate andis incident on the optical device 520 (the semi-transmissive mirror) isprovided, but a structure in which the light output from the imageforming devices 111A and 111B propagates through the air and is incidenton the optical device 520 may be provided. Further, the image formingdevice 211 described in Embodiment 3 may be used as the image formingdevice. Further, a configuration in which the light from the imageforming devices 111 and 211 arrives at the optical device 520 throughthe first polarizing units 130 and 330 may be provided, and aconfiguration in which the light from the image forming devices 111 and211 arrives at the optical device 520 directly may be provided.

Each of the image forming devices 111A and 111B is mounted on a frontportion 11, for example, using a screw. In addition, the member 521 ismounted on each of the image forming devices 111A and 111B, and theoptical device 520 (semi-transmissive mirror) is mounted on the member521. Because the display device of Embodiment 11 has substantially thesame configuration and structure as the display devices of Embodiments 1to 9 except for the differences described above, detailed descriptionthereof is omitted.

The preferred embodiments of the present disclosure have been describedabove, but the present disclosure is not limited to the aboveembodiments. The configurations and structures of the display devices(head mounted displays) and the image display devices described in theabove embodiments are exemplary and can be appropriately changed. Forexample, a surface relief hologram (see US 20040062505A1) may bearranged on the light guide plate. In the optical device 320, thediffraction grating element may be configured with a transmissivediffraction grating element, and alternatively, a form in which one ofthe first polarizing unit and the second polarizing unit is configuredwith a reflective diffraction grating element, and the other isconfigured with a transmissive diffraction grating element may beprovided. Alternatively, the diffraction grating element may beconfigured with a reflective blazed diffraction grating element. Thedetection of the light output from the image forming device by the lightreceiving device may be performed in conjunction with the measurement ofthe temperature of the light source constituting the image formingdevice.

Information or data related to an image to be displayed in the imageforming device may be stored in the display device, or information anddata may be recorded in a so-called cloud computer. In the latter case,the display device may be equipped with a communication device such as amobile telephone or a smartphone, or, combined with the communicationdevice so that various kinds of information or data can be transferredor exchanged between the cloud computer and the display device.

The embodiments have been described in connection with the example inwhich the image forming devices 111 and 211 display a single-color (forexample, green) image, but the image forming devices 111 and 211 candisplay a color image, and in this case, the light source may beconfigured with, for example, respective light sources that output red,green, and blue. Specifically, for example, it is preferable to obtainwhite light by mixing red, green, and blue light output from a red lightemitting element, a green light emitting element, and a blue lightemitting element using the light pipe and performing luminanceequalization. Here, when the light sources are configured with a redlight emitting semiconductor laser element, a green light emittingsemiconductor laser element, and a blue light emitting semiconductorlaser element, for a red image formed by the red light emittingsemiconductor laser element, a position of an image output from theimage forming device may be controlled based on the detection result ofthe light receiving device, and for green and blue images formed by thegreen light emitting semiconductor laser element and the blue lightemitting semiconductor laser element, a position of an image output fromthe image forming device may be controlled based on the detection resultof the light receiving device, or the wavelength of light output fromthe light sources may be controlled based on the detection result of thelight receiving device.

As a modified example of the image forming device, for example, an imageforming device of an active matrix type that includes a light emittingpanel in which light emitting elements 601, each of which is configuredwith a semiconductor laser element, are arranged in a 2D matrix as in aconceptual diagram illustrated in FIG. 17, and displays an image bycontrolling light emitting/non-light-emitting states of the lightemitting elements 601 and visualizing the light emitting states of thelight emitting element 601 directly may be provided. Light output fromthe image forming device is incident on the light guide plates 121 and321 through the collimating optical system 112. In the followingdescription, the light emitting element is configured with, for example,a semiconductor laser element.

Alternatively, as illustrated in a conceptual diagram of FIG. 18, acolor-display image forming device can include:

(α) a red light emitting panel 611R in which red light emitting elements601R for emitting red light are arranged in a 2D matrix;

(β) a green light emitting panel 611G in which green light emittingelements 601G for emitting green light are arranged in a 2D matrix;

(γ) a blue light emitting panel 611B in which blue light emittingelements 601B for emitting blue light are arranged in a 2D matrix; and

(δ) a unit (e.g., a dichroic prism 603) for integrating light outputfrom the red, green, and blue light emitting panels 611R, 611G, and 611Binto one optical path. Light emitting/non-light-emitting states of thered, green, and blue light emitting elements 601R, 601G, and 601B arecontrolled independently. Light output from this image forming device isalso incident on the light guide plate 121 or 321 via the collimatingoptical system 112. Reference numeral 612 denotes microlenses forcondensing light output from the light emitting elements.

Alternatively, a conceptual view of an image forming device includinglight emitting panels 611R, 611G, and 611B in which light emittingelements 601R, 601G, and 601B are arranged in a 2D matrix is illustratedin FIG. 19. Light output from the light emitting panels 611R, 611G, and611B is incident on a dichroic prism 603 after passage/non-passagethereof is controlled by light passage control devices 604R, 604G, and604B. The optical paths of the light beams are integrated into oneoptical path, and the light beams are incident on the light guide plate121 or 321 via the collimating optical system 112.

Alternatively, a conceptual view of an image forming device includinglight emitting panels 611R, 611G, and 611B and the like in which lightemitting elements 601R, 601G, and 601B are arranged in a 2D matrix isillustrated in FIG. 20. Light output from the light emitting panels611R, 611G, and 611B is incident on a dichroic prism 603 and opticalpaths thereof are integrated into one optical path. Passage/non-passageof the light output from the dichroic prism 603 is controlled by a lightpassage control device 604, and the light is incident on the light guideplate 121 or 321 via the collimating optical system 112.

Alternatively, as illustrated in FIG. 21, an image forming device caninclude a light emitting element 601R for emitting red light, a lightpassage control device (e.g., an LCD device 604R), which is a type oflight valve for controlling passage/non-passage of the red light outputfrom the light emitting element 601R, a light emitting element 601G foremitting green light, a light passage control device (e.g., an LCDdevice 604G), which is a type of light valve for controllingpassage/non-passage of the green light output from the light emittingelement 601G, a light emitting element 601B for emitting blue light, alight passage control device (e.g., an LCD device 604B), which is a typeof light valve for controlling passage/non-passage of the blue lightoutput from the light emitting element 601B, light guide members 602 forguiding the light output from the light emitting elements 601R, 601G,and 601B, and a unit (e.g., a dichroic prism 603) for integrating theoptical paths of the light into one optical path. The light output fromthe dichroic prism 603 is incident on the light guide plate 121 or 321via the collimating optical system 112.

Additionally, the present disclosure may also be configured as below.

[A01]«Image Display Device»

An image display device including:

(A) an image forming device;

(B) an optical device configured to receive incident light output fromthe image forming device and output the incident light; and

(C) a light receiving device configured to detect the light output fromthe image forming device.

[A02]«Image Display Device According to First Embodiment»

The image display device according to [A01],

wherein the optical device includes

-   -   (a) a light guide plate configured to cause the incident light        to propagate inside the light guide plate according to total        reflection and then output the incident light,    -   (b) a first polarizing unit configured to polarize the light        incident on the light guide plate so that the light incident on        the light guide plate is totally reflected inside the light        guide plate, and    -   (c) a second polarizing unit configured to polarize the light        propagating inside the light guide plate according to total        reflection to output part of light propagating inside the light        guide plate according to total reflection from the light guide        plate,    -   the second polarizing unit including        -   a first portion that polarizes the light propagating inside            the light guide plate according to total reflection toward            an observer, and        -   a second portion that polarizes the light propagating inside            the light guide plate according to total reflection toward            the light receiving device.

[A03]«Image Display Device According to Second Embodiment»

The image display device according to [A01],

wherein the optical device includes

-   -   (a) a light guide plate configured to cause the incident light        to propagate inside the light guide plate according to total        reflection and then output the incident light,    -   (b) a first polarizing unit configured to polarize the light        incident on the light guide plate so that the light incident on        the light guide plate is totally reflected inside the light        guide plate, and    -   (c) a second polarizing unit configured to polarize the light        propagating inside the light guide plate according to total        reflection to output part of light propagating inside the light        guide plate according to total reflection from the light guide        plate, and

wherein the light receiving device is arranged on an end portion of thelight guide plate at a side of the second polarizing unit.

[A04]

The image display device according to [A02] or [A03],

wherein the second polarizing unit is configured with a reflectivevolume hologram diffraction grating.

[A05]

The image display device according to any one of [A02] to [A04], whereinthe first polarizing unit is configured with a reflecting mirror, asemi-transmissive mirror, or a reflective volume hologram diffractiongrating.

[A06]«Image Display Device According to Third Embodiment»

The image display device according to [A01],

wherein the optical device includes a light semi-reflecting member thatreflects part of light output from the image forming device andtransmits a remaining part, and

wherein the light receiving device detects the light passing through thelight semi-reflecting member.

[A07]

The image display device according to [A06] wherein the lightsemi-reflecting member is configured with a semi-transmissive mirror, areflective volume hologram diffraction grating, or a semi-transmissiveconcave mirror.

[A8]

The image display device according to [A01],

wherein the light receiving device is optically connected to the opticaldevice.

[A09]

The image display device according to any one of [A01] to [A08],

wherein an operation of the image forming device is controlled based ona detection result of the light receiving device.

[A10]

The image display device according to [A09],

wherein a position of an image to be output from the image formingdevice is controlled based on the detection result of the lightreceiving device.

[A11]

The image display device according to [A09] wherein a signal forcompensating for distortion occurring in an image output from theoptical device is transmitted to the image forming device based on thedetection result of the light receiving device.

[A12]«Image Display Device According to Fourth Embodiment»

The image display device according to [A01],

wherein the image forming device includes a light source configured witha GaN semiconductor laser element,

wherein the optical device includes

-   -   (a) a light guide plate configured to cause the incident light        to propagate inside the light guide plate according to total        reflection and then output the incident light,    -   (b) a first polarizing unit configured to polarize the light        incident on the light guide plate so that the light incident on        the light guide plate is totally reflected inside the light        guide plate, the first polarizing unit being configured with a        reflecting mirror or a semi-transmissive mirror, and    -   (c) a second polarizing unit configured to polarize the light        propagating inside the light guide plate according to total        reflection to output part of light propagating inside the light        guide plate according to total reflection from the light guide        plate, the second polarizing unit being configured with a        reflective volume hologram diffraction grating,    -   the second polarizing unit including        -   a first portion that polarizes the light propagating inside            the light guide plate according to total reflection toward            an observer, and        -   a second portion that polarizes the light propagating inside            the light guide plate according to total reflection toward            the light receiving device, and

wherein a wavelength of light output from the light source is controlledbased on a detection result of the light receiving device.

[A13]«Image Display Device According to Fifth Embodiment»

The image display device according to [A01],

wherein the image forming device includes a light source configured witha GaN semiconductor laser element,

wherein the optical device includes

-   -   (a) a light guide plate configured to cause the incident light        to propagate inside the light guide plate according to total        reflection and then output the incident light,    -   (b) a first polarizing unit configured to polarize the light        incident on the light guide plate so that the light incident on        the light guide plate is totally reflected inside the light        guide plate, the first polarizing unit being configured with a        reflecting mirror or a semi-transmissive mirror, and    -   (c) a second polarizing unit configured to polarize the light        propagating inside the light guide plate according to total        reflection to output part of light propagating inside the light        guide plate according to total reflection from the light guide        plate, the second polarizing unit being configured with a        reflective volume hologram diffraction grating,

wherein the light receiving device is arranged on an end portion of thelight guide plate at a side of the second polarizing unit, and

wherein a wavelength of light output from the light source is controlledbased on a detection result of the light receiving device.

[A14]«Image Display Device According to Sixth Embodiment»

The image display device according to [A01],

wherein the image forming device includes a light source configured witha GaN semiconductor laser element,

wherein the optical device includes a light semi-reflecting member thatreflects part of light output from the image forming device andtransmits a remaining part, and

wherein the light receiving device detects the light passing through thelight semi-reflecting member, and controls a wavelength of light outputfrom the light source based on a detection result.

[A15]

The image display device according to [A14] wherein the lightsemi-reflecting member is configured with a semi-transmissive mirror, areflective volume hologram diffraction grating, or a semi-transmissiveconcave mirror.

[A16]

The image display device according to any one of [A01] to [A15],

wherein the light receiving device is configured in a manner that lightreceiving elements are arranged one-dimensionally or in a manner thatlight receiving elements are arranged in a two dimensional (2D) matrix.

[B01]«Display Device»

A display device including:

(I) a frame to be mounted on a head of an observer; and

(II) an image display device mounted on the frame,

-   -   the image display device including        -   (A) an image forming device,        -   (B) an optical device configured to receive incident light            output from the image forming device and outputs the            incident light, and        -   (C) a light receiving device configured to detect the light            output from the image forming device.

[B02]«Display Device»

A display device, including

(I) a frame mounted on a head of an observer, and

(II) an image display device mounted on the frame,

wherein the image display device is configured with the image displaydevice according to one of [A01] to [A16].

[C01]

An image display device including:

(A) an image forming device configured to include a liquid crystaldisplay device and a light source;

(B) a light guide plate configured to propagate light output from theimage forming device; and

(C) a light receiving device configured to detect part of light outputfrom the image forming device,

wherein a wavelength of light output from the light source is controlledbased on a detection result of the light receiving device.

[C02]

The image display device according to [C01],

wherein the light receiving device is arranged on an end portion of thelight guide plate.

[C03]

The image display device according to any one of [A01] to [A16], furtherincluding:

a light semi-reflecting member that reflects part of light output fromthe image forming device and transmits a remaining part,

wherein the light receiving device detects the light passing through thelight semi-reflecting member.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. An image display device comprising: an imageforming device; an optical device configured to receive incident lightoutput from the image forming device and output the incident light, theoptical device including a light guide plate configured to cause theincident light to propagate inside the light guide plate according tototal reflection and then output the incident light; a light receivingdevice arranged on a first surface of the light guide plate andconfigured to detect the light output from the optical device; and acontrol device configured to control an image output from the imageforming device based on a detection result from the light receivingdevice, wherein the optical device further includes: a first polarizingunit arranged on a second surface of the light guide plate andconfigured to polarize the light incident on the light guide plate sothat the light incident on the light guide plate is totally reflectedinside the light guide plate, and a second polarizing unit arranged onthe second surface of the light guide plate and configured to polarizethe light propagating inside the light guide plate according to totalreflection to output the light propagating inside the light guide plateaccording to total reflection from the light guide plate, wherein thelight receiving device is configured to detect an occurrence of anabnormality in the image display device based on an image detected bythe light receiving device, the image being detected based on the partof the light received by the light receiving device from the secondpolarizing unit, and wherein the first surface of the light guide plateand the second surface of the light guide plate face each other.
 2. Theimage display device according to claim 1, wherein the light receivingdevice is arranged on an end portion of the light guide plate at a sideof the second polarizing unit.
 3. The image display device according toclaim 1, wherein the optical device includes a light semi-reflectingmember that reflects part of light output from the image forming deviceand transmits a remaining part, and wherein the light receiving devicedetects the light passing through the light semi-reflecting member. 4.The image display device according to claim 1, wherein the lightreceiving device is optically connected to the optical device.
 5. Theimage display device according to claim 1, wherein an operation of theimage forming device is controlled based on the detection of theoccurrence of the abnormality in the image display device by the lightreceiving device.
 6. The image display device according to claim 5,wherein a position of an image to be output from the image formingdevice is controlled based on the detection of the occurrence of theabnormality in the image display device by the light receiving device.7. The image display device according to claim 1, wherein the imageforming device includes a light source configured with a GaNsemiconductor laser element, wherein the optical device includes a lightsemi-reflecting member that reflects part of light output from the imageforming device and transmits a remaining part, and wherein the lightreceiving device detects the light passing through the lightsemi-reflecting member, and controls a wavelength of light output fromthe light source based on the detection result.
 8. The image displaydevice according to claim 1, wherein the light receiving device isconfigured in a manner that light receiving elements are arrangedone-dimensionally or in a manner that light receiving elements arearranged in a two dimensional (2D) matrix.
 9. The image display deviceaccording to claim 1, wherein the detection of the occurrence of theabnormality in the image display device comprises detection of adeviation in a position of an image output from the image forming deviceand a position of the image detected by the light receiving device. 10.The image display device according to claim 1, wherein the secondpolarizing unit comprises: a first portion configured to polarize partof the light propagating inside the light guide plate according to totalreflection towards an observer, and a second portion configured topolarize part of the light propagating inside the light guide plateaccording to total reflection towards the light receiving devicearranged on the first surface of the light guide plate.
 11. A displaydevice comprising: a frame to be mounted on a head of an observer; andan image display device mounted on the frame, the image display deviceincluding: an image forming device, an optical device configured toreceive incident light output from the image forming device and outputthe incident light, the optical device including a light guide plateconfigured to cause the incident light to propagate inside the lightguide plate according to total reflection and then output the incidentlight, a light receiving device arranged on a first surface of the lightguide plate and configured to detect the light output from the opticaldevice; and a control device configured to control an image output fromthe image forming device based on a detection result from the lightreceiving device, wherein the optical device further includes: a firstpolarizing unit arranged on a second surface of the light guide plateand configured to polarize the light incident on the light guide plateso that the light incident on the light guide plate is totally reflectedinside the light guide plate, and a second polarizing unit arranged onthe second surface of the light guide plate and configured to polarizethe light propagating inside the light guide plate according to totalreflection to output the light propagating inside the light guide plateaccording to total reflection from the light guide plate, wherein thelight receiving device is configured to detect an occurrence of anabnormality in the image display device based on an image detected bythe light receiving device, the image being detected based on the partof the light received by the light receiving device from the secondpolarizing unit, and wherein the first surface of the light guide plateand the second surface of the light guide plate face each other.
 12. Animage display device comprising: an image forming device configured toinclude a liquid crystal display device and a light source; a lightguide plate configured to propagate light output from the image formingdevice; and a light receiving device arranged on a first surface of thelight guide plate and configured to detect part of light output from theoptical device; and a control device configured to control an imageoutput from the image forming device based on a detection result fromthe light receiving device, wherein a first polarizing unit is disposedinside the light guide plate, is arranged on a second surface of thelight guide plate, and is configured to polarize the light incident onthe light guide plate so that the light incident on the light guideplate is totally reflected inside the light guide plate, and a secondpolarizing unit is disposed inside the light guide plate, is arranged onthe second surface of the light guide plate, and is configured topolarize the light propagating inside the light guide plate according tototal reflection to output the light propagating inside the light guideplate according to total reflection from the light guide plate, whereinthe light receiving device is configured to detect an occurrence of anabnormality in the image display device based on an image detected bythe light receiving device, the image being detected based on the partof the light received by the light receiving device from the secondpolarizing unit, wherein a wavelength of light output from the lightsource is controlled based on the detection of the occurrence of theabnormality in the image display device by the light receiving device,and wherein the first surface of the light guide plate and the secondsurface of the light guide plate face each other.
 13. The image displaydevice according to claim 12, wherein the light receiving device isarranged on an end portion of the light guide plate.
 14. The imagedisplay device according to claim 12, further comprising: a lightsemi-reflecting member that reflects part of light output from the imageforming device and transmits a remaining part, wherein the lightreceiving device detects the light passing through the lightsemi-reflecting member.
 15. The image display device according to claim1, wherein a wavelength of light output from the image forming device iscontrolled based on the detection of the occurrence of the abnormalityin the image display device by the light receiving device.
 16. Thedisplay device according to claim 11, wherein a wavelength of lightoutput from the image forming device is controlled based on thedetection of the occurrence of the abnormality in the image displaydevice by the light receiving device.